It has been proposed to configure an image capturing apparatus such that an exit pupil of an imaging lens is divided into a plurality of pupil areas, and it is possible to simultaneously capture a plurality of parallax images depending on the divided pupil areas. PTL 1 includes a description about a defect caused by a short-circuit that may occur, when signals from PDs are read out via signal lines, between a signal line for reading out a signal from a PD corresponding to one of divided pupil areas and another signal line for reading out a signal from a PD corresponding to another pupil area. To handle the situation in which signals from two PDs are mixed in reading signals when signal lines are short-circuited, PTL 1 discloses a technique to detect a phase difference without using signals from a group of pixels having a defective signal line. In the technique disclosed in PTL 1, a recorded image is originally obtained by mixing image signals from two PDs, and thus an influence from defects described above does not occur.